the basics of booming and skimmingalaskarrt.org/files/mechanical and isb overview.pdfplatform acres...
TRANSCRIPT
The Basics of Booming and Skimming
Refers to the period of time during which conditions are appropriate for a particular response technology
Mostly a consideration for on-water response
It is a function of the type of oil, release rate, spreading, physical and chemical changes in the oil and environmental conditions
Amount of oil that can be concentrated and collected over time by an individual piece of equipment or system
Key factor in determining anticipated recovery
Applies to all on-water activities (not relevant to on-shore activities)
Function of oil thickness, application swath width and speed of advance
Encounter rate is low for containment (skimming or in-situ burning) and high for aerial dispersant operations
Decreases over time as oil spreads
Platform Acres per Hour
Mechanical
Small Skimmers 0.2 - 2.6
Medium Skimmers 3.5 - 14
Large Skimmers 21 - 70
In-Situ Burning 5 - 31
Dispersants
Vessels 28 - 140
Small Aircraft and Helicopters 193 - 893
Large Aircraft 1750 - 5000Source: ExxonMobil 2008a
Two steps ◦ Containment
◦ Recovery or removal
Boom configuration and placement ◦ U, V, J for two towing vessels
◦ Sweep (single vessel)
◦ Encirclement
◦ Diversion, exclusion or cascade
Source: ExxonMobil 2008
“U”
“V”
“J”
Source: ExxonMobil 2008
Booms limited by sea state and current ◦ Critical current for most booms
approximately 1 knot (0.5 m/s) ◦ Up to approximately 2 knots can be
accommodated with cascading booming
Sea State ◦ Good conditions - 0 to 10 knots, calm or swells ◦ Poor conditions - >20 knots, waves 3 to 4 foot
Boom size must be appropriate for conditions
Entrainment or drainage
Critical accumulation
Splash over
Submergence
Planing
Structural failure
Entrainment
Drainage
Splashover
Source: ExxonMobil 2008
Submergence
Planing
Source: ExxonMobil 2008
Mechanical devices to remove oil from water surface ◦ Independent
◦ Built into vessel or containment device
Function best on thick slicks
Rated based on recovery capacity as well as amount of water recovered with the oil
Major types of skimmers ◦ Oleophilic surface skimmers
◦ Weir skimmers
◦ Suction skimmers (vacuum devices)
◦ Elevating skimmers
◦ Submersion skimmers
◦ Vortex (centrifugal) skimmers
Special purpose ships
Drum Skimmer
Simple Weir Skimmer
Source: ExxonMobil 2008
Vertical Rope Skimmer
Vessel Mounted Sorbent Lifting Belt
Source: ExxonMobil 2008
Boom, pads, socks, pom-poms, etc.
Used for final cleanup
Synthetic
Natural ◦ Organic (peat moss, wood products)
◦ Inorganic (clay)
Can create secondary problems
Usually requires containment
Most oils will burn ◦ 2 to 3 mm thick
◦ Ignition is relatively easy
◦ May be necessary to break emulsions
◦ Usually very efficient (90% plus)
Smoke plume usually below health level concerns within 500m downwind
Rapid removal (eliminates need for storage)
Source: ExxonMobil 2008